Protective apparatus for preventing accumulation of ice on airfoils



March 2, I134s. E, E. HESTON 2,436,889

Filed June 9, 1944 Patented Mar. 2, 1.948

UNITED STATES 'Y PATENT oEEicE PROTECTIVE APPARATUS FOR PREVENT-v ING ACCUMULATION OF ICE ON AIRFOILS Eugene E. Heston, Akron, Ohio, assignor to The vB. F. Goodrich Company, New York, N. Y., a

corporation of New York Application June 9, 1944, serial No. 599,442

v1s claims. (c1. 244-134) This invention relates to protective apparatus for preventingthe accumulation of ice on a surface and especiallyto such apparatus suitable for installation upon airfoils, strutsA and other parts of aircraft and other structures used in ioingconditons, i .v Prior constructions o f inflatable-protective apparatus or covering having spanwise' tubes of relatively largey size, usually about two `or three inches in diameter, have not been wholly satisfactory under some icing conditions in preventing objectionable depositsof ice on the leading edges of wings and other vairfoils of aircraft. Such coverings have alsov caused objectionable vaerodynamic interference tothe smooth ow of structures exposed yto icingfconditions and especially vto provide -for breaking the bond of types of ice which heretofore have been diiiicult Ato remove; to providev for maintaining the desired aerodynamic,characteristics of such airfoils'and other structures; and to provide simplicity` of construction, lightweight and thinness of structure,

convenience of manufacture and installation, and

effectivenesskof operation.r

Other objects of th?, invention are'to provide vfor vaooniiguration of surface deformations in the covering for breaking the bond @fthe icedeposit thereon throughouta wide variety of icing conditionsnto provide for deforming the surface of such covering substantially throughoutv the Whole extent of the covering; to provide for preventing the entrapmentof air 'beneathy thecovering and the liftingof` the covering away from the airfoil or other structure at regions of low pressure; and to providefor deforming the covering only in the outward directionrelative to the surface of thel airfoil or other structure.

Morel Vspecific'object svof. the invention.. are to provide for distending the surfac'eofthe covering into small, sharply curvedridgesin the span.- wise directionorlthe choi'dwise directionor both directions; to provide a covering having a multi- Gf-B of Fig. 2, and

2 plicity of inflatable passages 'therein disposed in closely adjacent parallel relation; and to provide for securing the covering to the airfoil or other structure by adhesion substantially throughout the whole extent of such covering.

These and other objects and advantages of the invention will be apparentfrom the following description.

Inthe accompanying drawings which form a part of this specification, and in which like numerals are employed to designateV like parts throughout the same,

Fig. 1 is a perspective frontal view from above of apparatus or protective coverings mounted upon the leading edge of a wing of an aircraft and constructed in accordance with and embodying the invention, parts being broken away,

Fig. 2is a. plan view from above of the covering v before being mounted on the wing,

Fig, 3 is a sectional view of the covering taken along line 3`3 of Fig. 2,

Fig. 4 is a. view like Fig. 3 taken along line 4-/4 of Fig. 2,

Fig. 5y is a view'like Fig. 3 taken along line 5--5 of Fig. 2, I

Fig. 6 is aviewlikeFig, 3 taken along-line Fig'. 7 is a'view like Fig. 2 but showing a modied construction of the covering.

In the illustrative form of the invention shown in the drawings'protective coverings I0 and II are adapted tobe mounted upon the leading edge of a wing I2 of an aircraft I3, the wing being at.- tached to a fuselage I4 and having an engine nacelle I5, a propeller I6 and a landing light II or other structureV at such leading edge. The other wing and other airfoils, stabilizers, and struts, and other elements of the aircraft may Abe similarly provided, as. desired. Each of the coverings I0 land Il lare alike in their construction and arrangement except as to their span- Wise extent; hence'only the features of the covering I0 will be described in detail. 1

The covering Ill includes a body I8 of resilient rubber or other rubber-like material which may have embedded therein adjacent the inner supporting face I9 of the covering, a reinforcement `2li of suitable textile material such, for example,

as woven fabric of cotton, linen, rayon or other suitable material, straight laid or bias laid, for

.strengthening the covering and for preventing ob.-

jectionable stretching of the same. Also included in the body. It of the covering adjacent the outer stretchable face 2| thereof, are a multiplicity of inflatable passages or tubes 22,K 2 3of small diaieaese The tubes 22, 23 may be disposed to extendv wholly in the chordwise direction as shown especially in Fig. 7, or Wholly in the spanwise direc- 4 ameter than that of the tubes in another portion thereof.

In the construction shown especially in Figs. l to 6, inclusive, the covering I is shaped to accommodate the taper and the sweepback of the wing I2. The covering has a multiplicity of relatively small inflatable tubes, less than about three-quarters of an inch in diameter, and disposed in closely adjacent parallel relation, a part of the tubes 23 extending in the spanwise direction in. a portion 24 intermediate upper` and lower margins v25 and 26, respectively, of the covering and extending substantially to inboard and outboard end margins 21 and 28, respectively, of such tion, or may be disposed in part chordwi'se and in,A

part spanwise in any suitable arrangement thereof for obtaining the desired Washboard-like sur-` face-configuration of the covering as shown especially in Figs. and 6, whilemaintaining the desired aerodynamic characteristics of the airfoil or wing.

Whereas inflation tubes of prior constructions have been relatively large in size and have not been as effective as desired to remove ice under some conditions, as where the ice is strongly adhered to the covering surface at low temperatures, the tubes of the constructionr herein described are relatively small and are effective to break the bond of the ice'to the surface in cases where the l prior constructions have lacked full effectiveness', The success of the improved construction in breaking the strong bond of the ice results at least in part apparently from the relatively small radius of curvature of the tubes, causing a sufficiently sharp change of cont-our in the inlating operation and a sufficiently severe and concentrated disrupting force on the adhered ice. Also, the smallness of the tubes permits them to be arranged close together so that a number of tubes are operative on a small vzone ofice, and diverse directions of the disrupting forces are obtained Ona small area of ice spanning adjacent tubes.

As to the sizeof the tubes effective to produce the improved ice-removing action, excellent,` results have been obtained in constructions where the diameter of the tube passage has been on't'he order of a quarter of an inch, although goodresuits have been obtained alsojwith tubes up to,

about three-quarters of an inch in'diameter. Tube sizes greaterthan this have shown appreciably less effectiveness inv removing strongly bonded ice` in some cases.

The improvedaction of constructions utilizing the small tubes is noticeableespecially incases where the strongly adhered ice is deposited in a ,thin layer uponr the surface of `the covering.

Whereas larger tubes often have not demonstrated complete removal of such thin ice, and have required many inilations to break the bond of such 60 ice, the small tubes have shown eifectivenessgin ice promptly. This is advantageous especiall-y Abreaking the adhesion of and removing the thin v where aerodynamic cleanliness is desired at all times and it is desired to avoid letting the ice build upto greater thickness for easier breakage and removal.

The tubes may be uniform o-r varied as to size Within the above designated range in any suitable manner such, for example, as being of uniform diameter throughout the extent of the covering or throughout a portion of the latter, or alternate tubes being of' greater or lesser diameter than lthat of Ythe adjacent tubes, or the tubes inone portion ofthe covering being of 'a different dicovering. The covering Ill also has a part of the tubes 22 extending in the chordwise direction in Vrearward portions 29 and 30 of the covering and extending from the spanwise tubes 23 to substantially the upper and lower margins 25 and 2S.

Each ofthe chordwise tubes 22 in the `upper and the lower rearward portions'29 and 30 is less than about three-quarters of an inch in diameter and may be about'one-quaiter of an inch in diam eter.- For inflating purposes and to obtain the vdesired rocking action, the numerous small chordwise tubes in the upper and the lower rearward portions 29 and 3B are grouped into independent series, each Vseries comprising alternate tubes in communication, desirably at one of their ends, with an ihflatingmanfld or conduit 3|, 32, 33, 34 extending in the spa'nwise direction as shown `'especially in Figs. 2, 3 and 4, the manifolds 3| to V34 being disposed adjacent the margins 25 and 2S of the covering. Each manifold may beprovided` with a groovedA inner surface V35 for admitting air when the-manifold is inthe collapsed condition, and each manifold is connected desirably` at its inboard end to a supply conduit 36, 31, 38, 39 inv communication with a source of air under pressure in the fuselage I4, for example.

This constructionand'arrangement makes possible effectively-breaking the bond` ofV the ice deposited on such lportionsZtand 30 ofthe coveringand lifting the broken and-loosened lpieces of ice away from the covering by virtue-of the distending and rocking actions yof the tubes even thoughthe ice be very thin andtough, and facilitatesremoval ofthe-loosened pieces of ice thereon bythe scavenging actionof the Vrapid laminar flow offrair to the reariof'the stagnation point at the leading edge ofthe wing, andinaddition results in little"Y or no aerodynamicdisturbance to the flow of air across the wing since the chordwise 'tubes are substantiallyparallel to the direction of such flow. Ice-deposits of greater thickness arealso loosenedf'and'removed .thoroughly and promptly from the rearward portions 29 and 30,.by the distending, stretchingfand rocking actions of theV chordwise tubes-andthe ow of air 'thereoven Y Since the Aice deposited'on the covering may Vbe' relatively thick and cap-like in form inthe region of the stagnation point at the leading edge of the airfoil while being thinner` at rearward spa'nwis'e"tubes 23 may be of. ai lesser diameter, althoughA all such relatively small'spanwise' tubes 23'may beuniform in diameter within the range 4of sizes noted` hereinabove. 'For providing the lidc'esired rocking action and for ina'ting'purposs',

'with an in-ilating manifold or conduit 40 extending chordwise and the smaller diameter tubes being similarly in communication with an inflating manifoldor conduit 4| also extending chordwise. The manifolds 40 and 4| may be provided with a grooved inner surface like the other manifolds 3| to 34 and are connected to supply conduits 42 and 43 also in communication with the source of air under pressure. When the spanwise tubes 23 are inflated, they distend the outer stretchable face 2| of the covering into ridges of small radius of curvature substantially normal to the chordwise curvature of the leading edge of the airfoil thereby effectively breaking the bond of the ice-cap and lifting and rocking the latter for removal by the action of the flow of ambient air.

The fabric and rubber parts of the covering are preferably united by vulcanization under pressure. The respective margins 25, 26, 21 and 28 of the covering may be tapered in section for promoting smooth flow of'air over the covering, as shown especially in Figs. 3 and 4.

The coveringl is attached to the leading edge of the airfoil or wing I2 by being adhered to such wing continuously throughout the extent of the covering by a suitable adhesive such, for example,V as rubber cement. Such a mounting arrangement has the advantages of permitting substantially only outward expansion of the inflatable tubes for distending and stretching the outer stretchable face of the covering into the multiplicity vof ridges and of eliminating objectionable lifting of the covering from the airfoil at regions of lowpressure rearwardly of the leading edge. The lnecessity for additional'attaching structures such as metal reinforcing beads and fairing strips at the margins and for venting entrapped air-from the space beneath the covering are also obviated, hence simplifying the construction of such covering and facilitating providing lightweight and thinness of the structures of the covering. Y y ,Y

For inilating the relatively small passages or l tubes, an air pressure ofabout fifteen pounds per square inch has been found to be satisfactory, -although other suitable pressures, higher or lower may be used. In cyclically operating the protective covering I9, the spanwise tubes 23 are inflated first in the cycle and the chordwise tubes 22 are inflated next in the cycle. For one complete 4cycle of operation, for example, each ofthe independent series of spanwise tubes 23 is inflated alternately in a cyclical manner by admitting and exhausting the air under pressure to and from the `respective manifolds 40 and 4| through the re- Vspective supply conduits 42 and 43.` Then eachof the corresponding pairs of independent series of chordwise ltubes 22 in the upper and the lower rearward portions 29 and 30 is next inflated alternately in a cyclical manner by admitting and exhausting the air under pressure to and from the Lrespectivepairs of manifolds 3| and 33, 32 and 34 through the several pairs of supply conduits 36 and 38, 3l and 39, thereby completing one cycleof `operation of the covering. `In this manner the outer surface of the covering is distended outwardly and stretched 'into a multiplicity' 'of spanwise and chordwise ridges of small radius :of

lcurvature substantially throughout the wholeex- "tent of the' covering including the intermediatev portion 24 and the rearward portions 2'9 and 3U respectively, as shown especially by broken lines at 44-a`nd 45 in Fig. 5 and broken lines 46 in Fig. 6, thereby breaking effectively the bond of the ice deposited on such surface of the covering and rocking the pieces of ice on closely adjacent portions of the covering and thereby facilitating the` thorough and vprompt removal of the loosened' ice by the flow of yair across the leading edge of the wing.

Since the inflatable tubes are all of relatively small size and since the chordwise tubes are disposed vin the direction of laminar flow of air to the rear of thestagnatlon point, the arrangement results in low aerodnyamic disturbance to the flow of air across the wing thus maintaining 'the desired aerodynamic characteristics of such wing. Furthermore, since the covering is adhered to the wing throughout the whole extent of such covering, objectionable bulging and lifting away of the covering at regions of low pressure is effectively prevented which further facilitates maintaining the desired aerodynamic characteristics `of the wing; and such attachment of the covering to the'wing also eleminates andeifectively solves the dicult problem of venting the space between such covering and wing. A further advantage results from such an adhesive mounting of the covering in that such covering need not Vbe in a condition of stretch between Aattaching margins to prevent bulging and lifting and thus additional reinforcing means and fairing strips at the attaching margins are not required, resulting in a substantial saving in weight ,and simplified construction of the covering.

The modified construction 50 of the covering shown especially in Fig. 7 is like the construction "of the covering I0 `except that all relatively small inflatable passages or tubes 5| therein of less than about three-quarters of an inch in diameter and which may be about one-quarter of an inch in diameten'are'disposed wholly in the chordwisedi- Yrection in closely adjacent parallel relation. The multiplicity of chordwise tubes 5| extend continuously between upper and lower margins 52 and 53, respectively, and substantially from in Aboard'to outboard end margins 54l and 55, respec-` tively.' Forfinilating purposes and to obtain the manifold or conduit 56, -5'|. yand 5T may be disposed spanwise along the oppo. sitev margins 52 and 53 of the covering. Eachz manifold' may be provided with a grooved inner:

surface like that of the surface 35 of the manif- 'fold 3|, for example, of the covering IIJ; and each manifold 56, 51 is connected desirably at its inboard end to a'sup'ply conduit 59, 59 in communication with a suitable source of air under pressure. The covering 50 may be shaped to accommodate the taper and sweepback of the wing. The fabric and rubber parts of the covering 50 are preferably united by vulcanization under pressure. 'The covering 50 is adhered to the leading edge of the airfoil continuously throughout the extent of such covering by means of a suitable adhesive.

In the operation of the' covering 5|), each of the independent'series ofchordwise tubes 5| is indated in altern-ation with theother series of Asuch 'and 5'1" through the respective supplyconduit's 53.

of a multiplicity of sharply curved ridges at the:

surface of said covering as a result of the small cross-section of the passages for breaking the adhesiveV bond of an overlying ice-deposit, adjacent passages being disposed with their margins directly alongside one another in close parallel relation for effecting the surface action of said sharply curved ridges substantially com pletely over the group area of said passages.

7. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering of resilient rubberlike material having a multiplicity of inflatable tubular passages therein each of uniform diameter not exceeding three-quarters of an inch throughout its extent, to provide under inflation thereof a multiplicity of sharply curved ridges of uniform cross-section at the surface of said covering for breaking the adhesive bond of an overlying ice-deposit, adjacent passages being disposed with their margins directly alongside one another in close parallel relation for effecting the surface action of said sharply curved ridges substantially completely over the group area of said passages.

8. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering of resilient rubber'- like material having a multiplicity of inflatable tubes therein each of uniform diameternot exceeding three-quarters of an inch throughout its extent, to provide under inflation thereof a multiplicity of sharply curved ridges of uniform cross-section at the surface of said covering for breaking the adhesive bond of an overlying icedeposit, adjacent tubes being disposed with their walls in side-by-side abutting relation for effecting the surface action of said sharply curved ridges substantially completely over the group area of said tubes.

9. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering of resilient rubber-like material having in an intermediate portion thereof a group of inflatable tubular passages extending in the spanwise direction and having another group of inflatable tubular passages extending in the chordwise direction from said intermediate portion toward a margin of the covering, the passages of each group thereof being disposed in side-by-side parallel relation.

l0. Apparatus as defined in claim'9 in which the passages of said groups are each of uniform diameter not exceeding three-quarters of an inch, providing under inflation thereof a plurality of sharply curved ridges of uniform cross-section at the surface of said covering for breaking the adhesive bond of an overlying ice-deposit, adjacent passages of the respective groups thereof being disposed with the margins of the passages directly alongside one another in close parallel relation for effecting the surface action of said sharply curved ridges substantially completely over the group area of said passages.

11. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering of resilient rubber-like material having in a central portion thereof a group of inflatable tubular passages extending in the spanwise direction and having a group of inflatable tubular passages at each chordwise side of said central portion extending in the chordwise direction from said central portion toward a margin of the covering, the passages of each group thereof being disposed in side-by-side parallel relation.

12. Apparatus for preventing the accumulation of ice on a surface exposed to ice-forming conditions in airflow, Saidapparatus comprising a covering of elastic material for said surface including a front portion and a rearward portion and including a plurality of inflatable passages in said covering for distending said covering into a series of ridges, a plurality of passages in said rearward portion being disposed wholly within the latter said portion closely adjacent one another and all such passages in said rearward portion being of less width throughout their l lengths than a passage in said front portion of Vcluciing a front portion and a rearward portion and including a plurality of inflatable passagesk in'each of said portions for distending said covering into a series of ridges, said plurality of passages in said rearward portion being wholly disposed within the latter said portion closely adjacent one another and being individually of less width throughout their lengths than each of the passages within said front portion of the coverg ing whereby said covering is distensible into ridges relatively small and closely adjacent one another in said rearward portion as compared to the ridges in said front portion.

EUGENE E. RESTON.

REFERENCES CITED The following references are'of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,998,809 Geer Apr. 23, 1935 2,168,012 Waner Allg. 1, 1939 2,173,262 Monegan et a1. Sept. 19, 1939 2,327,034 Geer Aug. 17, 1943 

